Sub-zero temperatures for some centres in the South Island this afternoon

The temperature in Twizel will drop to -3C by this afternoon. Photo / Lynlee Officer

Sub-zero temperatures are sweeping down the South Island, with some areas plummeting to a chilly -3C this afternoon.

Inland parts of the South Island are especially cold, with temperatures at -3C in Middlemarch and in Twizel, while Cromwell is hovering closely behind at -2C.

Other parts of Southland, Otago and inland Canterbury are between 3C and 6C this afternoon.

The rest of the nation is hovering between 12C and 16C as of 1pm - a sign winter is truly here.

School holidays are off to a dry start but best plan for indoor activities with rain, gales and snow due to hit the country midweek.

MetService forecaster Tom Adams said the fine weather across most of New Zealand would last a couple more days before an approaching front made landfall.

This latest wintry blast would bring heavy rain to western regions in both islands, strong winds to central New Zealand and snow to the southern-most regions over Wednesday and Thursday.

"It's bringing a decent chunk of rain with it but what is quite exciting in this case is that it's coming far further south so there's reasonable chance of snow for the South Island," he said.

There was likely to be a decent amount of snowfall on Southern Lakes ski fields and the Southern Alps with the snow even affecting some higher alpine passes including the Milford Rd, the Crown Range Rd and Arthur's Pass.

Adams said the front was forecast to cross the South Island on Wednesday and make its way over the remainder of the country on Thursday.

The upper South Island and lower North Island would be pounded by potentially damaging northerly gales on Wednesday and Thursday.

There was a moderate risk of potentially damaging severe gales for inland parts of Southland to Canterbury, with a high risk for the Canterbury High Country, Marlborough, Wellington and southern Wairarapa.

The front was also expected to bring heavy rain to both islands stretching from Port Waikato through to Kapiti Coast in the North Island and the west coast of the South Island.

Adams said the wintry blast would sweep up the country in a matter of days and apart from showers the weather would improve by the weekend.